Apple iOS 10 Security Technical Implementation Guide

U_Apple_iOS_10_STIG_V1R3_Manual-xccdf.xml

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2017-02-14

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This Security Technical Implementation Guide is published as a tool to improve the security of Department of Defense (DoD) information systems. The requirements are derived from the National Institute of Standards and Technology (NIST) 800-53 and related documents. Comments or proposed revisions to this document should be sent via email to the following address: [email protected]

Vuln

Rule

Version

CCI

Severity

Title

Description

SV-86397r1_rule

AIOS-01-080002

CCI-000057

MEDIUM

Apple iOS must lock the display after 15 minutes (or less) of inactivity.

The screen lock timeout must be set to a value that helps protect the device from unauthorized access. Having a too-long timeout would increase the window of opportunity for adversaries who gain physical access to the mobile device through loss, theft, etc. Such devices are much more likely to be in an unlocked state when acquired by an adversary, thus granting immediate access to the data on the mobile device. The maximum timeout period of 15 minutes has been selected to balance functionality and security; shorter timeout periods may be appropriate depending on the risks posed to the mobile device.
SFR ID: FMT_SMF_EXT.1.1 #01b

SV-86399r1_rule

AIOS-01-080004

CCI-000205

LOW

Apple iOS must enforce a minimum password length of six characters.

Password strength is a measure of the effectiveness of a password in resisting guessing and brute force attacks. The ability to crack a password is a function of how many attempts an adversary is permitted, how quickly an adversary can do each attempt, and the size of the password space. The longer the minimum length of the password is, the larger the password space. Having a too-short minimum password length significantly reduces password strength, increasing the chance of password compromise and resulting device and data compromise.
SFR ID: FMT_SMF_EXT.1.1 #01a

SV-86401r1_rule

AIOS-01-080005

CCI-000044

LOW

Apple iOS must not allow more than 10 consecutive failed authentication attempts.

The more attempts an adversary has to guess a password, the more likely the adversary will enter the correct password and gain access to resources on the device. Setting a limit on the number of attempts mitigates this risk. Setting the limit at 10 gives authorized users the ability to make a few mistakes when entering the password but still provides adequate protection against dictionary or brute force attacks on the password.
SFR ID: FMT_SMF_EXT.1.1 #02

SV-86403r1_rule

AIOS-01-080006

CCI-002476

HIGH

Apple iOS must require a valid password be successfully entered before the mobile device data is unencrypted.

Passwords provide a form of access control that prevents unauthorized individuals from accessing computing resources and sensitive data. Passwords may also be a source of entropy for generation of key encryption or data encryption keys. If a password is not required to access data, this data is accessible to any adversary who obtains physical possession of the device. Requiring that a password be successfully entered before the mobile device data is unencrypted mitigates this risk.
Note: MDF PP v2.0 requires a Password Authentication Factor and requires management of its length and complexity. It leaves open whether the existence of a password is subject to management. This STIGID addresses the configuration to require a password, which is critical to the cybersecurity posture of the device.
SFR ID: FIA_UAU_EXT.1.1

SV-86405r1_rule

AIOS-01-080007

CCI-000366

LOW

Apple iOS must not allow passwords that include more than two repeating or sequential characters.

Password strength is a measure of the effectiveness of a password in resisting guessing and brute force attacks. Passwords that contain repeating or sequential characters are significantly easier to guess than those that do not contain repeating or sequential characters. Therefore, disallowing repeating or sequential characters increases password strength and decreases risk.
SFR ID: FMT_SMF_EXT.1.1 #01b

SV-86407r1_rule

AIOS-02-080002

CCI-000366

MEDIUM

Apple iOS must not allow backup to remote systems (iCloud).

Backups to remote systems (including cloud backup) can leave data vulnerable to breach on the external systems, which often offer less protection than the MOS. Where the remote backup involves a cloud-based solution, the backup capability is often used to synchronize data across multiple devices. In this case, DoD devices may synchronize DoD-sensitive information to a user's personal device or other unauthorized computers that are vulnerable to breach. Disallowing remote backup mitigates this risk.
SFR ID: FMT_SMF_EXT.1.1 #40

Backups to remote systems (including cloud backup and cloud document syncing) can leave data vulnerable to breach on the external systems, which often offer less protection than the MOS. Where the remote backup involves a cloud-based solution, the backup capability is often used to synchronize data across multiple devices. In this case, DoD devices may synchronize DoD-sensitive information to a user's personal device or other unauthorized computers that are vulnerable to breach. Disallowing remote backup mitigates this risk.
SFR ID: FMT_SMF_EXT.1.1 #40

SV-86411r1_rule

AIOS-02-080004

CCI-000366

MEDIUM

Apple iOS must not allow backup to remote systems (iCloud Keychain).

The iCloud Keychain is an Apple iOS function that will store users' account names and passwords in iCloud and then synchronize this data among the users' Macs, iPhones, and iPads. An adversary may use any of the stored iCloud keychain passwords after unlocking one of the synchronized devices. If a user is synchronizing devices, the user must protect all of the devices to prevent unauthorized use of the passcodes. Moreover, the keychain being transmitted through the cloud opens the possibility that a well-resourced, sophisticated adversary could compromise the cloud-transmitted keychain. Not allowing the iCloud Keychain feature mitigates the risk of the encrypted set of passwords being compromised when transmitted through the cloud or synchronized across multiple devices.
SFR ID: FMT_SMF_EXT.1.1 #40

SV-86413r1_rule

AIOS-02-080005

CCI-000366

MEDIUM

Apple iOS must not allow backup to remote systems (My Photo Stream).

When My Photo Stream is enabled, sensitive photos will be uploaded automatically to Apple-specified servers and available on other Apple iOS devices associated with the same Apple ID, provided that the other device also has My Photo Stream enabled. This potentially places sensitive photos on a server outside of DoD's control and potentially makes them available to non-DoD devices. Disabling My Photo Stream mitigates this risk.
SFR ID: FMT_SMF_EXT.1.1 #40

SV-86415r1_rule

AIOS-02-080006

CCI-000366

MEDIUM

Apple iOS must not allow backup to remote systems (iCloud Photo Sharing, also known as Shared Photo Streams).

When iCloud Photo Sharing is enabled, sensitive photos will be uploaded automatically to Apple-specified servers and available on the Apple IOS devices of other users who have accepted invitations to participate in iCloud Photo Sharing. This potentially places sensitive photos on a server outside of DoD's control and potentially makes them available to non-DoD users and devices. Disabling iCloud Photo Sharing mitigates this risk.
SFR ID: FMT_SMF_EXT.1.1 #40

SV-86417r1_rule

AIOS-02-080007

CCI-000381

LOW

Apple iOS must disable automatic transfer of diagnostic data to an external device other than an MDM service with which the device has enrolled.

Many software systems automatically send diagnostic data to the manufacturer or a third party. This data enables the developers to understand real-world field behavior and improve the product based on that information. Unfortunately, it can also reveal information about what DoD users are doing with the systems and what causes them to fail. An adversary embedded within the software development team or elsewhere could use the information acquired to breach mobile operating system security. Disabling automatic transfer of such information mitigates this risk.
SFR ID: FMT_SMF_EXT.1.1#45

SV-86419r1_rule

AIOS-02-080008

CCI-000366

LOW

Apple iOS must implement the management setting: limit Ad Tracking.

Ad Tracking refers to the advertisers' ability to categorize the device and spam the user with ads that are most relevant to the user's preferences. By not "Force limiting ad tracking", advertising companies are able to gather information about the user and device's browsing habits. If "Limit Ad Tracking" is not limited, a database of browsing habits of DoD devices can be gathered and stored under no supervision of the DoD. By limiting ad tracking, this setting does not completely mitigate the risk, but it limits the amount of information gathering.
SFR ID: FMT_SMF_EXT.1.1 #45

SV-86421r1_rule

AIOS-02-080009

CCI-000062

MEDIUM

Apple iOS must not display notifications when the device is locked.

Many mobile devices display notifications on the lock screen so users can obtain relevant information in a timely manner without having to frequently unlock the phone to determine if there are new notifications. However, in many cases, these notifications can contain sensitive information. When they are available on the lock screen, an adversary can see them merely by being in close physical proximity to the device. Configuring the MOS to not send notifications to the lock screen mitigates this risk.
SFR ID: FMT_SMF_EXT.1.1 #21

SV-86423r1_rule

AIOS-02-080010

CCI-000062

MEDIUM

Apple iOS must not display notifications (calendar information) when the device is locked.

Many mobile devices display notifications (including calendar information) on the lock screen so users can obtain relevant information in a timely manner without having to frequently unlock the phone to determine if there are new notifications. However, in many cases, these notifications can contain sensitive information. When they are available on the lock screen, an adversary can see them merely by being in close physical proximity to the device. Configuring the MOS to not send notifications to the lock screen mitigates this risk.
SFR ID: FMT_SMF_EXT.1.1 #21

SV-86425r1_rule

AIOS-02-080011

CCI-000366

MEDIUM

Apple iOS must not include applications with the following characteristics: Siri when the device is locked.

On Apple iOS devices, users can access the device's contact database or calendar to obtain phone numbers and other information using a human voice even when the mobile device is locked. Often this information is Personally Identifiable Information (PII), which is considered sensitive. It could also be used by an adversary to profile the user or engage in social engineering to obtain further information from other unsuspecting users. Disabling access to the contact database and calendar in these situations mitigates the risk of this attack. The AO may waive this requirement with written notice if the operational environment requires this capability.
SFR ID: FMT_SMF_EXT.1.1 #10b

SV-86427r1_rule

AIOS-02-080012

CCI-000366

MEDIUM

Apple iOS must not include applications with the following characteristics: Voice dialing application if available when MD is locked.

On Apple iOS devices, users can access the device's contact database or calendar to obtain phone numbers and other information using a human voice even when the mobile device is locked. Often this information is Personally Identifiable Information (PII), which is considered sensitive. It could also be used by an adversary to profile the user or engage in social engineering to obtain further information from other unsuspecting users. Disabling access to the contact database and calendar in these situations mitigates the risk of this attack.
SFR ID: FMT_SMF_EXT.1.1 #10b

SV-86429r1_rule

AIOS-02-080013

CCI-000366

MEDIUM

Apple iOS must be configured to disable Touch ID.

Many mobile devices now permit a user to unlock the user's device by presenting a fingerprint to an embedded fingerprint reader. Other biometrics and token-based systems are feasible as well. None of these alternatives are currently evaluated in a Common Criteria evaluation of a mobile device against the Security Target based on the Mobile Device Fundamentals Protection Profile. Many have known vulnerabilities. Until there are DoD-approved assurance activities to evaluate the efficacy of these alternatives, they are significant potential vulnerabilities to DoD information and information systems. Disabling them mitigates the risk of their use. Touch ID is a fingerprint reader that has been installed on some models of Apple iOS devices.
SFR ID: FMT_SMF_EXT.1.1 #45b

SV-86431r1_rule

AIOS-02-080014

CCI-000366

MEDIUM

Apple iOS must not allow non-DoD applications to access DoD data.

Managed apps have been approved for the handling of DoD-sensitive information. Unmanaged apps are provided for productivity and morale purposes but are not approved to handle DoD-sensitive information. Examples of unmanaged apps include apps for news services, travel guides, maps, and social networking. If a document were to be viewed in a managed app and the user had the ability to open this same document in an unmanaged app, this could lead to the compromise of sensitive DoD data. In some cases, the unmanaged apps are connected to cloud backup or social networks that would permit dissemination of DoD-sensitive information to unauthorized individuals. Not allowing data to be opened within unmanaged apps mitigates the risk of compromising sensitive data.
SFR ID: FMT_SMF.1.1 #42

The AutoFill functionality in the Safari web browser allows the user to complete a form that contains sensitive information, such as PII, without previous knowledge of the information. By allowing the use of the AutoFill functionality, an adversary who learns a user's Apple iOS device passcode, or who otherwise is able to unlock the device, may be able to further breach other systems by relying on the AutoFill feature to provide information unknown to the adversary. By disabling the AutoFill functionality, the risk of an adversary gaining further information about the device's user or compromising other systems is significantly mitigated.
SFR ID: FMT_SMF_EXT.1.1 #45

When syncing an Apple iOS device to a computer running iTunes, iTunes will prompt the user to back up the Apple iOS device. If the performed backup is not encrypted, this could lead to the unauthorized disclosure of DoD-sensitive information if non-DoD personnel are able to access that machine. By forcing the backup to be encrypted, this greatly mitigates the risk of compromising sensitive data. iTunes backup and USB connections to computers are not authorized, but this control provides defense-in-depth for cases in which a user violates policy either intentionally or inadvertently.
SFR ID: FMT_SMF_EXT.1.1 #45

SV-86465r1_rule

AIOS-02-080101

CCI-000366

LOW

Apple iOS must not allow backup to remote systems (enterprise books).

Enterprise books may contain DoD-sensitive information. When enterprise books are backed up, they are vulnerable to attacks on the backup systems and media. Disabling the backup capability mitigates this risk. If such books are lost, accidentally deleted, or corrupted for any reason, they can be easily retrieved from the original source.
SFR ID: FMT_SMF_EXT.1.1 #45

SV-86467r1_rule

AIOS-02-080102

CCI-000366

LOW

Apple iOS must implement the management setting: not allow use of Handoff.

Handoff permits a user of an Apple iOS device to transition user activities from one device to another. Handoff passes sufficient information between the devices to describe the activity, but app data synchronization associated with the activity is handled though iCloud, which should be disabled on a compliant Apple iOS device. If a user associates both DoD and personal devices to the same Apple ID, the user may improperly reveal information about the nature of the user's activities on an unprotected device. Disabling Handoff mitigates this risk.
SFR ID: FMT_SMF_EXT.1.1 #45

Apple iOS must implement the management setting: require the user to enter a password when connecting to an AirPlay-enabled device for the first time.

When a user is allowed to use AirPlay without a password, there is the potential that it may mistakenly associate the Apple iOS device with an AirPlay-enabled device other than the one intended (i.e., by choosing the wrong one from the AirPlay list displayed). This creates the potential that someone in control of a mistakenly associated device may obtain DoD-sensitive information without authorization. Requiring a password before such an association mitigates this risk. Passwords do not require any administration, nor must they comply with any complexity requirements.
SFR ID: FMT_SMF_EXT.1.1 #40

Apple iOS device must have the latest available iOS operating system installed.

Required security features are not available in earlier OS versions. In addition, there are known vulnerabilities in earlier versions.
SFR ID: FMT_SMF_EXT.1.1 #45

SV-86491r1_rule

AIOS-03-080101

CCI-000366

MEDIUM

Apple iOS must implement the management setting: use SSL for Exchange ActiveSync.

Exchange email messages are a form of data in transit and thus are vulnerable to eavesdropping and man-in-the-middle attacks. Secure Sockets Layer (SSL), also referred to as Transport Layer Security (TLS), provides encryption and authentication services that mitigate the risk of breach.
SFR ID: FMT_SMF_EXT.1.1 #45

SV-86493r1_rule

AIOS-03-080102

CCI-000366

MEDIUM

Apple iOS must implement the management setting: not allow messages in an ActiveSync Exchange account to be forwarded or moved to other accounts in the Apple iOS Mail app.

The Apple iOS Mail app can be configured to support multiple email accounts concurrently. These email accounts are likely to involve content of varying degrees of sensitivity (e.g., both personal and enterprise messages). To prevent the unauthorized and undetected forwarding or moving of messages from one account to another, Mail ActiveSync Exchange accounts can be configured to block such behavior. While users may still send a message from the Exchange account to another account, these transactions must involve an Exchange server, enabling audit records of the transaction, filtering of mail content, and subsequent forensic analysis.
SFR ID: FMT_SMF_EXT.1.1 #45

SV-86495r1_rule

AIOS-05-080001

CCI-000366

MEDIUM

Apple iOS must implement the management setting: Treat Airdrop as an unmanaged destination.

An Airdrop feature is a way to send contact information or photos to other users with this same feature enabled. This feature enables a possible attack vector for adversaries to exploit. Once the attacker has gained access to the information broadcast by this feature, he/she may distribute this sensitive information very quickly and without DoD's control or awareness. By disabling this feature, the risk of mass data exfiltration will be mitigated.
Note: If the site uses Apple's optional Device Enrollment Program (DEP), this control is available as a supervised MDM control.
SFR ID: FMT_SMF_EXT.1.1 #45

SV-86497r1_rule

AIOS-05-080101

CCI-000366

MEDIUM

Apple iOS must implement the management setting: not have any Family Members in Family Sharing.

Apple's Family Sharing service allows Apple iOS users to create a Family Group whose members have several shared capabilities, including the ability to lock, wipe, play a sound on, or locate the Apple iOS devices of other members. Each member of the group must be invited to the group and accept that invitation. A DoD user's Apple iOS device may be inadvertently or maliciously wiped by another member of the Family Group. This poses a risk that the user could be without a mobile device for a period of time or lose sensitive information that has not been backed up to other storage media. Configuring Apple iOS devices so their associated Apple IDs are not members of Family Groups mitigates this risk.
Note: If the site uses Apple's optional Device Enrollment Program (DEP), this control is available as a supervised MDM control.
SFR ID: FMT_SMF_EXT.1.1 #45

SV-86499r1_rule

AIOS-05-080102

CCI-000366

MEDIUM

Apple iOS must implement the management setting: not share location data through iCloud.

Sharing of location data is an operations security (OPSEC) risk because it potentially allows an adversary to determine a DoD user's location and movements and patterns in those movements over time. An adversary could use this information to target the user or to gather intelligence on the user's likely activities. Using commercial cloud services to store and handle location data could leave the data vulnerable to breach, particularly by sophisticated adversaries. Disabling the use of such services mitigates this risk.
SFR ID: FMT_SMF_EXT.1.1 #45

When a device is unenrolled from MDM, it is possible to relax the security policies that the MDM had implemented on the device. This may cause apps and data to be more vulnerable than they were prior to enrollment. Removing managed apps (and consequently the data they maintain) upon unenrollment mitigates this risk because on appropriately configured Apple iOS devices, DoD-sensitive information exists only within managed apps.
SFR ID: FMT_SMF_EXT.1.1 #45

Configuration profiles define security policies on Apple iOS devices. If a user is able to remove a configuration profile, the user can then change the configuration that had been enforced by that policy. Relaxing security policies may introduce vulnerabilities that the profiles had mitigated. Configuring a profile to never be removed mitigates this risk.
SFR ID: FMT_SMF_EXT.1.1 #45

SV-86505r1_rule

AIOS-11-080201

CCI-000097

MEDIUM

Apple iOS must not allow backup to locally connected systems.

Data on mobile devices is protected by numerous mechanisms, including user authentication, access control, and cryptography. When the data is backed up to an external system (either locally connected or cloud-based), many if not all of these mechanisms are no longer present. This leaves the backed-up data vulnerable to attack. Disabling backup to external systems mitigates this risk.
SFR ID: FMT_SMF_EXT.1.1 #40

SV-86507r1_rule

AIOS-11-080202

CCI-000366

MEDIUM

Apple iOS must wipe protected or sensitive data upon unenrollment from MDM.

When a mobile device is no longer going to be managed by MDM technologies, its protected/sensitive data must be sanitized because it will no longer be protected by the MDM software, so it is at much greater risk of unauthorized access and disclosure.
SFR ID: FMT_SMF_EXT.2.1

Because Apple Watch is a personal device, it is key that any sensitive DoD data displayed on the Apple Watch not be viewable when the watch is not in the immediate possession of the user. This control ensures the Apple Watch screen locks when the user takes the watch off, thereby protecting sensitive DoD data from possible exposure.
SFR ID: FMT_SMF_EXT.1.1 #45

SV-86513r1_rule

AIOS-98-080208

CCI-000366

LOW

Before establishing a user session, Apple iOS must display an administrator-specified advisory notice and consent warning banner regarding use of the mobile operating system.

To facilitate the legal monitoring of mobile devices and investigations pertaining to those devices, the MOS is required to display the DoD-approved system use notification message or banner before granting access to the system. System use notification messages can be displayed when individuals unlock the device. The approved DoD text must be used as specified in KS referenced in DoDI 8500.01.
The mobile operating system is required to display the DoD-approved system use notification message or banner before granting access to the system that provides privacy and security notices consistent with applicable federal laws, Executive Orders, directives, policies, regulations, standards, and guidance. Required banners help ensure that DoD can audit and monitor the activities of mobile device users without legal restriction.
System use notification messages can be displayed when individuals first access or unlock the mobile device. The banner must be implemented as a "click-through" banner at device unlock (to the extent permitted by the operating system). A "click through" banner prevents further activity on the information system unless and until the user executes a positive action to manifest agreement by clicking on a box indicating "OK".
The approved DoD text must be used exactly as required in the KS referenced in DoDI 8500.01. For devices accommodating banners of 1300 characters, the banner text is:
You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only.
By using this IS (which includes any device attached to this IS), you consent to the following conditions:
-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.
-At any time, the USG may inspect and seize data stored on this IS.
-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.
-This IS includes security measures (e.g., authentication and access controls) to protect USG interests--not for your personal benefit or privacy.
-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details.
For devices with severe character limitations, the banner text is:
I've read & consent to terms in IS user agreem't.
The administrator must configure the banner text exactly as written without any changes.
SFR ID: FTA_TAB.1.1

SV-86955r1_rule

AIOS-01-100100

CCI-000366

MEDIUM

Apple iOS must be configured to wipe all sensitive DoD data (Controlled Unclassified Information (CUI)/For Official Use Only (FOUO)) and Personally Identifiable Information (PII) data during a remote wipe command from the MDM server.

DoD sensitive data (CUI/FOUO) or PII data downloaded from DoD web sites via Safari will be saved by default in a non-managed app on a DoD iOS device. If the device is wiped via an MDM Enterprise remote wipe command, data saved in non-managed apps will not be deleted and may be accessible to unauthorized people that have access to the MDM-wiped device. If the device is wiped via a Full Device MDM remote wipe command, all data on the device, including managed and unmanaged, will be deleted, but a Full Device wipe may not be appropriate for devices that have been authorized for personal use and have personal data stored on them or are BYOD devices. The risk in not using a Full Device wipe can be mitigated if a Managed Domain Configuration profile is installed on all managed iOS devices that contains a list of all DoD web domains that may have sensitive DoD data (CUI/FOUO) and PII data (primarily DoD web domains that require DoD PKI authentication credentials to access the web site).
SFR ID: FMT_SMF_EXT.1.1 #9, 19, 28, 45g